Arriva occasionally use them on the "swanline", the service which stops at every station on the line from Cardiff to Swansea, on a 153 that takes about 75 minutes so really wouldn't appreciate being on a 142 for that long.
The longest journey i've been on a 142 was from Cardiff to Maesteg as there was a signalling failure at severn tunnel junction so the train from gloucester was delayed.. unfortunately this 142 apparently couldn't go above second gear so all in all it took far longer than it should have.
They're really not much fun to ride when at full capacity (or more) at rush hour.. bring back the class 37 hauled trains!
(off topic,
http://www.youtube.com/watch?v=0GwOzaUZ_ZE is a video of a class 37 going through my local station.. about 2 minutes walk away)